Effect on South American CL: This proposal would split our Basileuterus
bivittatus into two species, with recognition of northern roraimae as
a separate species.

Background: The bird we treat as one species, Basileuterus
bivittatus (Two-banded Warbler), has a disjunct distribution, with one
subspecies group in the Tepui region of (mostly) Venezuela and the other in the
Andes from southern Peru to northern Argentina. This follows the traditional
classification (e.g., Hellmayr 1935, Meyer de Schauensee 1966, 1970, Lowery
& Monroe 1968, Meyer de Schauensee & Phelps 1978, Ridgely & Tudor
1989, Curson et al. 1994, Sibley & Monroe 1990).

The
subspecies roraimae is very similar in plumage to nominate bivittatus,
differing primarily in a "cleaner" head pattern, with more sharply
defined orange coronal stripe and black lateral stripes. The
southernmost subspecies argentinae could be considered the most
divergent of the three in that its coronal stripe is bright yellow, not orange.
LSUMZ material from depto. Santa Cruz shows that the population there is
actually a mix of yellow and orange-crowned birds.

New information: Hilty (2003) treated roraimae as a
separate species from bivittatus without explanation.

Analysis: The plumage differences between roraimae and bivittatus
are less, in many cases far less, than those between many taxa currently
treated as same subspecies in Basileuterus. Without any vocal evidence,
this one has no evidence to even vaguely support it other than the
"disjunct "distribution. But "how disjunct" do
distributions have to be to be used as criteria for defining species limits?
[Tangentially .... classifying distributions into "disjunct" and
"not disjunct" is one of the worst cases I know of inflicting a
typology on a continuum. Most species' ranges consist of many "slightly
disjunct" populations -- it all depends on the geographic scale at which
they are examined. The presumed conceptual meaning of "disjunct" is
something like "so far apart that there is no current gene flow,"
but that can happen on opposite sides of severe barriers like rivers and
mountains over distances of less than a kilometer that would not normally be
described as "disjunct."]

Recommendation: I vote "NO" on this proposal. Only a
quantitative study of vocalization differences, if they exist, would convince
me on this one.

SIBLEY, C. G., AND B. L.
MONROE, JR. 1990. Distribution and taxonomy of birds of the World. Yale
University Press, New Haven, Connecticut.

Van Remsen, October 2003

Comments from Robbins: "Given that there isn't any new
information I vote "no". As Van points out, we need at least some
data to support a split."

Comments from Jaramillo: "NO -- Since there is no new information
they need to stay under one species. I bet they are two however."

Comments from Zimmer: "I vote "NO". As with many
previous proposals, I think we need some published rationale."

Comments from Stiles: "NO pending publication of solid
evidence. As in many other such cases, this will probably prove to be correct
but I do not believe in changing things without published evidence."